Rebels in Syria have burned and looted the religious sites of minorities, Human Rights Watch said on Wednesday, as the longest and deadliest of the Arab Spring revolts becomes increasingly sectarian.

The 22-month-old rebellion against President Bashar al-Assad started as a peaceful protest movement but has turned into civil war, pitting mostly Sunni Muslim rebels against a state security and military establishment dominated by Assad’s minority Alawite sect, an offshoot of Shi’ite Islam.

In the northern Idlib province, where rebels have taken swathes of territory from government forces, the New York-based rights group said opposition fighters destroyed a Shi’ite “husseiniya” – a religious site devoted to Hussein, a martyr in Shi’ite tradition.

A video published online showed rebels hoisting assault rifles in the air and cheering as the site in the village of Zarzour, taken by rebels in December, burned in the background.

In the video, which Reuters cannot independently verify, one man announces the “destruction of the dens of the Shi’ites and Rafida,” a derogatory term used against Shi’ites.